We received three and a half inches of much needed rain here in Huntingdon County this week. I expected this volume of moisture would produce a good crop of a standby of local mushroom pickers, the Meadow Mushroom or Agaricus campestris. But I decided yesterday to head out into the woods rather than visit a couple of places where I know they grow. An old friend of mine lives along the road into the woods I planned to hunt so I stopped for a brief visit on my way there. We chatted a bit and when I told him I was going mushroom hunting he asked me if I wanted the mushrooms growing in his yard. Well, yeah, he had my interest.
He pointed me to the area and there were several partial fairy rings of A. campestris, one of which is shown in the first photo below. A fairy ring is a circular growth of mushrooms formed when mushroom mycelium starts at a single point and expands outward. If the growth medium is homogenous or uniform, then the mycelium grows at an equal rate to form a near perfect circle of growth. The mushroom fruiting bodies tend to arise only from the outer edge of the circle, forming an open ring of mushrooms. In days past this growth pattern was not understood and folks were puzzled by these rings of mushrooms that appeared seemingly overnight after a rain. One whimsical theory is that the rings were a sign that fairies had danced in the circle during the night. A. campestris is almost always found in lawns and similar grassy areas and since these areas tend to be quite uniform the mushrooms frequently grow in these ring patterns. If the circle is interrupted by some obstacle to growth then an arc or partial ring is formed.
One telling characteristic can be seen in the photo. The stem of A. campestris is quite short and they grow low to the ground. Any white mushroom with a longer stem, growing well off the ground is not A. campestris and should be avoided, at least until it can be positively identified. One beautiful white mushroom that could be mistaken for A. campestris if this rule is not followed is the very poisonous Amanita virosa, the subject of a previous blog. As always, it's critical to know intimately any mushroom you plan to eat, and any look-alikes to it.
As noted, the Meadow Mushroom is a common favorite of mushroom hunters. It's easy to spot in open lawns, relatively easy to identify, and more flavorful than it's cousin the common store-bought white button mushroom. Several stages of growth of A. campestris are shown in the second photo below. In all cases the cap is white but sometimes takes on tones of brown or grey. The flesh is white, but sometimes discolors brownish or reddish in age. The odor is very mushroomy. In the upper center row are a couple of buttons still closed. Proceeding clockwise around the photo you can note the cottony veil and the pink gill color of the young mushrooms. This veil sometimes forms an annulus or ring on the stem as shown in the center lower row. This annulus is not very durable however and as the photo shows may not be in evidence as the mushroom matures. As the mushroom ages the shape becomes flattened and the gills darken to a deep chocolate brown. The gills are close and free of the stem at maturity. These specimens were collected two days after the rain and already quite a range of maturity can be seen.
For more information refer to Bill Russell's book or most any field guide. I will note in closing that Bill suggests a good reason to maintain a chemical free lawn, not that one should be needed. If you avoid chemicals and scatter the trimmings of A. campestris in your yard you likely will be able to harvest the mushrooms from your own mushroom garden in subsequent years. A wild mushroom feast doesn't get much easier than that.